This invention relates to a radio receiver and an electronic timepiece that receive radio waves transmitted from positioning satellites.
In related art, there are electronic timepieces that receive radio waves transmitted from positioning satellites of a global navigation satellite system (GNSS) to obtain date and time and a position. Such an electronic timepiece amplifies, converts the frequencies of, and filters the received radio waves by RF (radio frequency) circuits, and demodulates and decodes the radio waves in a demodulated signal process to obtain necessary information.
In reception of radio waves transmitted from positioning satellites, there are specific circumstances in which satellite signals of transmitted radio waves that can be received need to be quickly searched for and acquired from radio waves transmitted from multiple positioning satellites and in which these acquired satellite signals need to be obtained in parallel. A receiver having sufficient sensitivity is therefore required for performing such operations. Thus, a high gain and a low noise figure (NF) are required of RF circuits mounted in the electronic timepiece. As a result, power consumed by the RF circuits has a significant influence on the power consumption of the entire electronic timepiece. There have therefore been attempts to reduce power consumption of RF circuits as part of reduction in power consumption of electronic timepieces.
JP 2009-300274 A that is a Japanese patent document, for example, discloses a receiver that interrupts power supply to RF circuits after acquisition of satellite signals and supplies power to the RF circuits only at timings at which necessary information can be obtained so as to reduce power consumption.
Reception conditions of radio waves from positioning satellites, however, greatly change depending on the receiver environments. Hence uniform reception operation where the reception conditions are not considered may disadvantageously consume power in excess.
This invention is directed to a radio receiver and an electronic timepiece capable of optimizing power consumption depending on reception conditions of radio waves transmitted from positioning satellites.